TechnoBuffalo has leaked an internal document which seems to show that Sprint's LTE deployment is further along than expected. Back in January Sprint announced that Atlanta, Dallas, Houston, and San Antonio would be its first LTE markets by "mid 2012." Reporting for TB, Mark Hearn surmises that Sprint has already started testing its next-generation network in Akron, Chicago, Fort Worth, Nashville, New York, and the California towns of Rialto and Stockton. Sprint began the upgrade as early as August last year in Nashville, and from the chart it appears some work has been completed ahead of schedule.

It's impossible to know how long Sprint's internal tests will take, or indeed if the chart is accurate, but it seems logical. Sprint recently detailed its plans to offer LTE coverage to 123 million people this year, expanding to 250 million by the end of 2013. We'll keep you updated on any official announcements regarding Sprint's LTE rollout.